The present invention relates to a medical instrument for an endoscope to be passed through a medical instrument insert channel of an endoscope in use, and used for dissection or exsection of mucous tunics of anatomy by distributing high-frequency current.
A medical instrument for an endoscope generally has a structure in which a distal electrode to which high-frequency current can be distributed is projected forward from the distal end of an electrically insulating sheath, whereby mucous tunics or the like which is in contact with the distal electrode is dissected by Joule heat by distributing high-frequency current to the distal electrode which is pressed against the surface of the mucous tunics.
However, when the distal portion of the endoscope is significantly displaced because an operator touches a curved operating knob of the endoscope or because a patient harrumphs and hence the anatomy side is suddenly moved during the operation of high-frequency medical treatment, an unscripted portion of the anatomy may accidentally be dissected.
As a countermeasure to this problem, in the related art, there is a device in which the distal electrode is formed by a flexible metallic strand wire or the like so that the movement of the distal electrode with respect to a diseased part does not occur abruptly, even when the positional relationship between the distal end of the endoscope and the anatomy changes unexpectedly. (For example, JP-A-2002-153484)
When the distal electrode is formed of the metallic strand wire, the distal electrode does not come apart from the dissected portion owing to bending motion of the distal electrode as long as the change of the positional relationship between the distal end of the endoscope and the anatomy is within a certain range, and hence a phenomenon in which dissection of the unscripted portion of the anatomy can be prevented from occurring.
However, when the positional relationship between the distal end of the endoscope and the anatomy is changed unexpectedly by more than several centimeters, the change cannot be absorbed by such bending motion of the distal electrode, and hence there is a risk for dissecting the unscripted portion of the anatomy.
Another kind of a medical instrument for an endoscope is known which is a beak-shaped medical instrument for an endoscope configured in such a manner that a pair of beak-shaped electrodes which are connected to a high-frequency power supply and open and close like a beak by remote control at the proximal end of a sheath are disposed at the distal end of the sheath which is to be inserted into and removed from the medical instrument insert channel of an endoscope. (for example, JP-A-2000-271128)
When performing dissection or the like of anatomy with a beak-shaped medical instrument for an endoscope, an operation including the steps of clamping the anatomy with the beak-shape electrodes to which high-frequency current is distributed, dissecting the same, advancing the instrument a little, closing the same again, and dissecting the same is repeated.
However, when the positional relationship between the distal end of the endoscope and the anatomy is moved unexpectedly and significantly because a patient harrumphs or an operator erroneously operates a curved operating knob of the endoscope when the beak-shaped electrodes are opened or completely closed during such high-frequency operation, it takes a lot of trouble to performing a guiding operation for restoring the beak-shaped electrodes accurately to a portion to be dissected of the diseased part, and hence dissection or exsection of the anatomy may not be performed smoothly.